Composite building panels, consisting of two parallel facing sheets disposed in spaced relation and having a core of foam material between them, have been produced for some time. One method of producing such a panel involves depositing foam on one facing sheet and allowing it to cure while in contact with the sheet so that the foam and the sheet adhere to each other. Then building paper is positioned over the expanding foam and the other facing sheet is then laminated to the building paper. When the facing sheets are relatively flexible members, they can be positioned in a generally continuous process. On the other hand, if the sheets are rigid, present processes require the manual handling of the sheets by trained operators--a relatively expensive operation.
Also, it has been found that a bonded joint between foam and a facing sheet is not as strong as a joint formed during the expansion and curing of foam against a facing sheet. Several patents, such as the patents to Potchen et al., U.S. Pat. No. 2,866,730; the patent to Schroter et al., U.S. Pat. No. 3,560,285; the patent to Roberts et al., U.S. Pat. No. 4,037,006; and the patent to Jones, U.S. Pat. No. 4,043,719 disclose processes in which foam is allowed to expand into gripping relation with two facing members during a continuous panel-forming operation. However, in these processes, at least one of the facing sheets is a relatively flexible, bendable member such as heavy paper, aluminum foil, or roofing paper as in Jones, U.S. Pat. No. 4,043,719 or fiber-glass reinforced resin as in Potchen et al., U.S. Pat. No. 2,866,730. In such panels the foam core, not the bendable facing sheet, is relied on to resist bending loads imposed on the panels.
U.S. Patents to Turnbull, U.S. Pat. No. 3,446,692; Bolster et al., U.S. Pat. No. 3,510,391; and Timbrook, U.S. Pat. No. 3,665,662 disclose building panels involving foam cores disposed between two facing sheets. None of these patents discloses a continuous method of forming the panels in a process that involves the expansion of the foam into adhering relation with both sheets. Accordingly, an object of this invention is to provide such a process and an apparatus for carrying it out.